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Re: deprecate implicit MX even for IPv4

2008-04-07 13:51:41

At 04:40 -0400 on 04/07/2008, Hector Santos wrote about Re: deprecate implicit MX even for IPv4:

Michael Storz wrote:

The longer I follow this discussion and think about it, I am feeling that
the cleanest solution would be to deprecate implicit MX even for IPv4. In
the meantime I am convinced the implizit MX is a defect of RFC 2821. It
was introduced more than 20 years ago as a workaround to get the routing
via explizit MX RRs running.

 > snip

Therefore from an operational and liability standpoint it is time to
deprecate the implizit MX RR. You had the guts to the deprecation the
source routes some years back. Now have the guts to deprecate the implizit

Well, from a liability standpoint, in my view, eliminating the IMPLICIT MX can certainly be viewed as the WRONG direction.

How does replacing the use of the A record with a MX pointing at the A record signify a wrong direction? My MTA will still be locatable via the MX record and able to locate the other MTA by its MX record so the messages will still get delivered. If, for some reason, one of the MTAs is running some antiquated code that does not recognize the use of the MX record to locate what MTA to send to, it will still (in violation of the implicate MX elimination) have a A record to use (unless when the MX record gets defined the A record for the FQDN gets deleted and the MX is pointed to something other than its FQDN name). If the MTA goes IPv6-Only or Dual Stack (with the MX not pointing at an A record with the FQDN name) this antiquated MTA would fail anyway.